USB connectors

Sam Staton · #1 03-15-2012, 04:30 PM

I would like to install built-in USB jacks into my panel to support my iPad & my iPhone. I have obtained stand-alone USB jacks, but I have found an issue with Apple's implimentation of the USB standard for charging. Apparently, unless there is a certain voltage present on the two data wires, the devices will not charge. Does anyone on the forum have any info on this? I believe that if I can determine what the voltages need to be, I can design a circuit board to present the proper voltages. Thanks in advance!

pczar3 · #2 03-15-2012, 08:16 PM

From what I can find, it is a standard USB interface on the devices. The only problem I see is that it takes a high current device to charge the IPad. Normal USB ports are limited in the current they can supply (somewhere around 500 ma.) The normal IPad charger can supply up to 2 amperes. If you chase around the Apple technical documents you will find the specs. Here is the link I found:

https://developer.apple.com/library/...2644-TPXREF101

Good Luck,
Paul

jdeas · #3 03-16-2012, 08:03 AM

http://en.wikipedia.org/wiki/Univers...rging_adapters

Before the battery charging specification was defined, there was no standardized way for the portable device to inquire how much current was available. For example, Apple's iPod and iPhone chargers indicate the available current by voltages on the D- and D+ lines. When D+ = D- = 2V, the device may pull up to 500 mA. When D+ = 2.0 V and D- = 2.8 V, the device may pull up to 1000 mA of current.[45]

flion · #4 03-16-2012, 08:18 AM

I did a quick search on sparkfun expecting to find a board but the only thing I found went the other way: USB power to charge a battery, not system power to USB. On the other hand, I found this (http://www.sparkfun.com/products/8638) and at $5 I wouldn't hesitate to cannibalize it and hook it up behind a panel in place of a dedicated 'lighter-style' power port. I have a similar device in my pickup that I run my Zune MP3 player and sometimes my laptop off of (it has both USB and 2-prong jacks) and have seen no problems with overcharging the MP3 player in continuous use.

mrreddick · #5 03-16-2012, 08:25 AM

I installed a USB port made by Belkin that puts out the REQUIRED 2 amp power to keep your iPad charged while in flight. Best source is eBay but you can get one at stores like Best Buy, Fry's, Radio Shack, etc.

RVbySDI · #6 03-16-2012, 10:34 AM

Quote:

Originally Posted by mrreddick

I installed a USB port made by Belkin that puts out the REQUIRED 2 amp power to keep your iPad charged while in flight. Best source is eBay but you can get one at stores like Best Buy, Fry's, Radio Shack, etc.

Mike,
Do you have a part number or any other identifier for this Belkin part?

mrreddick · #7 03-17-2012, 08:54 AM

Quote:

Originally Posted by RVbySDI

Mike,
Do you have a part number or any other identifier for this Belkin part?

Steve, any 12V receptacle will work. I mounted mine behind the panel and I already had a suitable grommeted hole from a previous gps installation that the usb end of an iPad cable would fit through. The key is in the adapter you plug in to the receptacle. There are many, many available, some with two usb ports and US sellers. Just go to ebay.com and search for iPad car charger and take your pick. Most are under $5 with free shipping. I've been using my setup for over a year with absolutely no problems.

Sam Staton · #8 03-17-2012, 12:37 PM

This is essentially what I was looking for. Since my ports will be fused off of ship's power, current isn't an issue. I'll fuse for 3A, and set the interface for the +2 & +2.8 and see what happens. Thanks guys!